Effects of single genetic variants and polygenic obesity risk scores on disordered eating in adolescents - The HUNT study

Linkage and association of variants in the dopamine receptor 2 gene (DRD2) with polycystic ovary syndrome

Polycystic ovarian syndrome (PCOS) is a disorder with a foundation of neuroendocrine dysfunction, characterized by increased gonadotropin-releasing hormone (GnRH) pulsatility, which is antagonized by dopamine. The dopamine receptor 2 (DRD2), encoded by the DRD2 gene, has been shown to mediate dopamine's inhibition of GnRH neuron excitability through pre- and post-synaptic interactions in murine models. Further, DRD2 is known to mediate prolactin (PRL) inhibition by dopamine, and high blood level of PRL have been found in more than one third of women with PCOS. We recently identified PRL as a gene contributing to PCOS risk and reported DRD2 conferring risk for type 2 diabetes and depression, which can both coexist with PCOS. Given DRD2 mediating dopamine's action on neuroendocrine profiles and association with metabolic-mental states related to PCOS, polymorphisms in DRD2 may predispose to development of PCOS. Therefore, we aimed to investigate whether DRD2 variants are in linkage to and/or linkage disequilibrium (i.e., linkage and association) with PCOS in Italian families. In 212 Italian families, we tested 22 variants within the DRD2 gene for linkage and linkage disequilibrium with PCOS. We identified five novel variants significantly linked to the risk of PCOS. This is the first study to identify DRD2 as a risk gene in PCOS, however, functional studies are needed to confirm these results.

Risk factors for eating disorders: findings from a rapid review

BACKGROUND

Risk factors represent a range of complex variables associated with the onset, development, and course of eating disorders. Understanding these risk factors is vital for the refinement of aetiological models, which may inform the development of targeted, evidence-based prevention, early intervention, and treatment programs. This Rapid Review aimed to identify and summarise research studies conducted within the last 12 years, focusing on risk factors associated with eating disorders.

METHODS

The current review forms part of a series of Rapid Reviews to be published in a special issue in the Journal of Eating Disorders, funded by the Australian Government to inform the development of the National Eating Disorder Research and Translation Strategy 2021-2031. Three databases were searched for studies published between 2009 and 2021, published in English, and comprising high-level evidence studies (meta-analyses, systematic reviews, moderately sized randomised controlled studies, moderately sized controlled-cohort studies, or population studies). Data pertaining to risk factors for eating disorders were synthesised and outlined in the current paper.

RESULTS

A total of 284 studies were included. The findings were divided into nine main categories: (1) genetics, (2) gastrointestinal microbiota and autoimmune reactions, (3) childhood and early adolescent exposures, (4) personality traits and comorbid mental health conditions, (5) gender, (6) socio-economic status, (7) ethnic minority, (8) body image and social influence, and (9) elite sports. A substantial amount of research exists supporting the role of inherited genetic risk in the development of eating disorders, with biological risk factors, such as the role of gut microbiota in dysregulation of appetite, an area of emerging evidence. Abuse, trauma and childhood obesity are strongly linked to eating disorders, however less conclusive evidence exists regarding developmental factors such as role of in-utero exposure to hormones. Comorbidities between eating disorders and mental health disorders, including personality and mood disorders, have been found to increase the severity of eating disorder symptomatology. Higher education attainment, body image-related factors, and use of appearance-focused social media are also associated with increased risk of eating disorder symptoms.

CONCLUSION

Eating disorders are associated with multiple risk factors. An extensive amount of research has been conducted in the field; however, further studies are required to assess the causal nature of the risk factors identified in the current review. This will assist in understanding the sequelae of eating disorder development and in turn allow for enhancement of existing interventions and ultimately improved outcomes for individuals.

An examination of potential mediators of the relationship between polygenic scores of BMI and waist circumference and phenotypic adiposity

Objective: The present study examined whether physical activity, personality, cognition, education, and depressive symptoms mediate the association between polygenic scores (PGS) for body mass index (BMI) and waist circumference and the corresponding phenotypic adiposity measures.Design: Participants were 9,139 individuals aged 50 to 107 years (57% women; Mean Age: 68.17, SD: 10.06) from the Health and Retirement Study who were genotyped. Trained staff measured their height, weight, and waist circumference, and participants answered questions on physical activity, personality, education, cognitive function, and depressive symptoms.Main Outcome Measures: BMI and waist circumference.Results: A higher PGS for both BMI and waist circumference were related to higher phenotypic BMI and waist circumference, respectively, in part through their association with lower physical activity, conscientiousness, education, and higher depressive symptoms but not cognition. The mediators accounted for 6.6% of the association between PGS and BMI and 9.6% of the association between PGS and waist circumference.Conclusion: The present study provides new evidence on the multiple, distinct pathways through which genetic propensity to higher BMI and waist circumference may lead to higher adiposity in adulthood. Individuals with a higher genetic predisposition to obesity may gain more weight through less adaptive behavioral, personality and educational profiles.

Genetic Basis of Obesity and Type 2 Diabetes in Africans: Impact on Precision Medicine

PURPOSE OF REVIEW

Recent advances in genomics provide opportunities for novel understanding of the biology of human traits with the goal of improving human health. Here, we review recent obesity and type 2 diabetes (T2D)-related genomic studies in African populations and discuss the implications of limited genomics studies on health disparity and precision medicine.

RECENT FINDINGS

Genome-wide association studies in Africans have yielded genetic discovery that would otherwise not be possible; these include identification of novel loci associated with obesity (SEMA-4D, PRKCA, WARS2), metabolic syndrome (CA-10, CTNNA3), and T2D (AGMO, ZRANB3). ZRANB3 was recently demonstrated to influence beta cell mass and insulin response. Despite these promising results, genomic studies in African populations are still limited and thus genomics tools and approaches such as polygenic risk scores and precision medicine are likely to have limited utility in Africans with the unacceptable possibility of exacerbating prevailing health disparities. African populations provide unique opportunities for increasing our understanding of the genetic basis of cardiometabolic disorders. We highlight the need for more coordinated and sustained efforts to increase the representation of Africans in genomic studies both as participants and scientists.

A biopsychosocial approach to processes and pathways in the development of overweight and obesity in childhood: Insights from developmental theory and research

Childhood obesity has reached alarming proportions in many countries. There is consensus that both biological (especially genetic) and environmental (including psychosocial) factors contribute to weight gain and obesity in childhood. Research has identified extensive risk or predictive factors for childhood obesity from both of these domains. There is less consensus about the developmental processes or pathways showing how these risk factors lead to overweigh/obesity (OW/OB) in childhood. We outline a biopsychosocial process model of the development of OW/OB in childhood. The model and associated scholarship from developmental theory and research guide an analysis of research on OW/OB in childhood. The model incorporates biological factors such as genetic predispositions or susceptibility genes, temperament, and homeostatic and allostatic processes with the psychosocial and behavioral factors of parenting, parental feeding practices, child appetitive traits, food liking, food intakes, and energy expenditure. There is an emphasis on bidirectional and transactional processes linking child biology and behavior with psychosocial processes and environment. Insights from developmental theory and research include implications for conceptualization, measurement, research design, and possible multiple pathways to OW/OB. Understanding the developmental processes and pathways involved in childhood OW/OB should contribute to more targeted prevention and intervention strategies in childhood.

Role of eating disorders-related polymorphisms in obesity pathophysiology

Human biological system provides innumerable neuroendocrine inputs for food intake control, with effects on appetite's modulation and the satiety signs. Its regulation is very complex, engaging several molecular interactions with many tissues, hormones, and neural circuits. Thus, signaling molecules that control food intake are critical for normal energy homeostasis and a deregulation of these pathways can lead to eating disorders and obesity. In line of this, genetic factors have a significantly influence of the regulation of neural circuits controlling the appetite and satiety pathways, as well as the regulation of brain reward systems. Single Nucleotide Polymorphisms (SNPs) in genes related to hypothalamic appetite and satiety mechanisms, further in multiple neurotransmitter systems may contribute to the development of major Eating Disorders (EDs) related to obesity, among them Binge Eating Disorder (BED) and Bulimia Nervosa (BN), which are discussed in this review.

Biological and Psychosocial Processes in the Development of Children's Appetitive Traits: Insights from Developmental Theory and Research

There has been increasing concern expressed about children's food intakes and dietary patterns. These are closely linked to children's appetitive traits (such as disinhibited eating and food fussiness/neophobia). Research has examined both biological and psychosocial correlates or predictors of these traits. There has been less focus on possible processes or mechanisms associated with children's development of these traits and research that links biological and psychosocial factors. There is an absence of research that links biological and psychosocial factors. In the present article, we outline a model intended to facilitate theory and research on the development of appetitive traits. It is based on scholarship from developmental theory and research and incorporates biological factors such as genetic predispositions and temperament as well as psychosocial factors in terms of parent cognitions, feeding styles and feeding practices. Particular attention is directed to aspects such as emotional eating and feeding, self-regulation of energy intake, and non-shared family environments. We highlight the opportunity for longitudinal research that examines bidirectional, transactional and cascade processes and uses a developmental framework. The model provides a basis for connecting the biological foundations of appetitive traits to system-level analysis in the family. Knowledge generated through the application of the model should lead to more effective prevention and intervention initiatives.